46643d1 · streamly · git.iko.soy

git.iko.soy/streamly

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Add lastN combinator

46643d1adithyaov7 years ago

benchmark/Linear.hs+4

compare with master

unifiedsplit

@@ -24,6 +24,7 @@ import qualified Streamly.Memory.Array as A

24import qualified Streamly.Prelude as S

25import qualified Streamly.Internal.Data.Sink as Sink

27+import qualified Streamly.Internal.Memory.Array as IA

27import qualified Streamly.Internal.Data.Fold as IFL

28import qualified Streamly.Internal.Data.Fold as IFL

28import qualified Streamly.Internal.Prelude as IP

29import qualified Streamly.Internal.Prelude as IP

29import qualified Streamly.Internal.Data.Pipe as Pipe

30import qualified Streamly.Internal.Data.Pipe as Pipe

@@ -200,6 +201,9 @@ main =

200 -- this is too low and causes all benchmarks reported in ns

201 -- this is too low and causes all benchmarks reported in ns

201 -- , benchIOSink "head" Ops.head

202 -- , benchIOSink "head" Ops.head

202 , benchIOSink "last" Ops.last

203 , benchIOSink "last" Ops.last

204+ , benchIOSink "lastN.1" (S.fold (IA.lastN 1))

205+ , benchIOSink "lastN.10" (S.fold (IA.lastN 10))

206+ , benchIOSink "lastN.Max" (S.fold (IA.lastN Ops.maxValue))

203 -- , benchIOSink "lookup" Ops.lookup

207 -- , benchIOSink "lookup" Ops.lookup

204 , benchIOSink "find" Ops.find

208 , benchIOSink "find" Ops.find

205 , benchIOSink "findIndex" Ops.findIndex

209 , benchIOSink "findIndex" Ops.findIndex

src/Streamly/Internal/Data/Stream/StreamD.hs+23

@@ -305,6 +305,10 @@ module Streamly.Internal.Data.Stream.StreamD

305 , mkParallel

306 , applyParallel

307 , foldParallel

308+

309+ -- XXX Move this later

310+ -- XXX Exported from Array again

311+ , lastN

308 )

312 )

309where

313where

310

314

@@ -346,6 +350,7 @@ import Streamly.Internal.Data.Fold.Types (Fold(..))

346import Streamly.Internal.Data.Pipe.Types (Pipe(..), PipeState(..))

350import Streamly.Internal.Data.Pipe.Types (Pipe(..), PipeState(..))

347import Streamly.Internal.Data.Time.Clock (Clock(Monotonic), getTime)

351import Streamly.Internal.Data.Time.Clock (Clock(Monotonic), getTime)

348import Streamly.Internal.Data.Unfold.Types (Unfold(..))

352import Streamly.Internal.Data.Unfold.Types (Unfold(..))

353+import Streamly.Internal.Data.Strict (Tuple3'(..))

349

354

350import Streamly.Internal.Data.Stream.StreamD.Type

355import Streamly.Internal.Data.Stream.StreamD.Type

351import Streamly.Internal.Data.SVar

356import Streamly.Internal.Data.SVar

@@ -4013,3 +4018,21 @@ tapAsync f (Stream step1 state1) = Stream step TapInit

4013 Yield a s -> Yield a (TapDone s)

4018 Yield a s -> Yield a (TapDone s)

4014 Skip s -> Skip (TapDone s)

4019 Skip s -> Skip (TapDone s)

4015 Stop -> Stop

4020 Stop -> Stop

4021+

4022+-- XXX Is there room for improvement?

4023+-- | Take last 'n' elements from the stream and discard the rest.

4024+{-# INLINABLE lastN #-}

4025+lastN :: (Storable a, MonadIO m) => Int -> Fold m a (Array a)

4026+lastN n = Fold step initial done

4027+ where

4028+ step (Tuple3' rb rh i) a = do

4029+ rh1 <- liftIO $ RB.unsafeInsert rb rh a

4030+ return $ Tuple3' rb rh1 (i + 1)

4031+ initial = fmap (\(a, b) -> Tuple3' a b 0) $ liftIO $ RB.new n

4032+ done (Tuple3' rb rh i) = do

4033+ arr <- liftIO $ A.newArray n

4034+ foldFunc i rh snoc' arr rb

4035+ snoc' b a = liftIO $ A.unsafeSnoc b a

4036+ foldFunc i

4037+ | i < n = RB.unsafeFoldRingM

4038+ | otherwise = RB.unsafeFoldRingFullM

src/Streamly/Internal/Memory/Array.hs+3

@@ -124,6 +124,9 @@ module Streamly.Internal.Memory.Array

124 -- * Folding Arrays

125 , streamFold

126 , fold

127+

128+ -- * Folds with Array as the container

129+ , D.lastN

127 )

130 )

128where

131where

129

132